The invention relates to a brake device for an automobile and, more particularly, a vehicle-mounted brake device for generating a braking force by using an electric power.
Hitherto, a brake device for generating a braking force by making electrically driven motors operative has been known. For example, according to the brake device proposed in JP-A-11-321599, a vehicle motion controller transmits a required braking force to a drive controller in accordance with an output of a pedal sensor for detecting depression quantity of a brake pedal, an output of a thrust sensor for detecting a thrust of an actuator, and an output of a wheel speed sensor, and a frictional material is pressed onto a disk rotor by the actuator which is driven by the drive controller, thereby applying the braking force to wheels.
According to the brake device, advanced vehicle controls such as anti-lock control, automatic brake control, and the like and an adjustment of a brake feeling can be performed in correspondence to software. A parking brake can be also applied by using an actuator for vehicle control in common.
According to the conventional brake device, the vehicle motion controller and the drive controller are arranged on the vehicle body side (hereinafter, referred to as a spring-mass) of a vehicle having suspensions. The spring-mass is constructed by a body, an engine and a transmission which are mounted on the body, the interior, and the like. The actuator, thrust sensor, and wheel speed sensor are arranged on the wheel side (hereinafter, referred to as a unspring-mass) which is interlocked with a vertical displacement of the wheel or a motion of a steering when the vehicle body is fixed. The unspring-mass is constructed by a suspension, a knuckle, an axle, the wheel, and the like.
The drive controller and the actuator, the vehicle motion controller and the thrust sensor, and the vehicle motion controller and the wheel speed sensor are connected by electric wires, respectively. A relative displacement occurs between the spring-mass and the unspring-mass due to the motion of the suspension or the steering. Since the displacement is absorbed by deformation of the electric wires, the electric wires between the spring-mass and the unspring-mass require excellent flexibility. In addition to it, since a strength is also required in terms of countermeasures against a stone hit and freezing, a special electric wire called a bending cable is used as an electric wire. An expensive resin is also used as a sheath of the wire. A connector having excellent waterproof is necessary in a connecting portion of the electric wire and this becomes a cause of an increase in costs.
According to the conventional brake device, three bending cables for connecting the drive controller and the actuator, the vehicle motion controller and the thrust sensor, and the vehicle motion controller and the wheel speed sensor are wired with respect to each wheel, so that there is a waste of cost. A troublesomeness of wiring and the number of fixing parts which are used also increase, so that they also exert an influence on the costs. In the case where a DC brushless motor or an AC motor is used for the actuator, since a large alternating current is supplied between the drive controller and the actuator, there is a risk that noises are introduced into an ambient analog signal lines. Therefore, a cost for taking a countermeasure against the noises is needed and this exercises an influence on the costs.
It is an object of the invention to provide a cheap brake device by reducing a cost of a bending cable.
The above object is accomplished by a construction such that a drive controller is attached onto an actuator side and communication with a vehicle motion controller which is arranged on the vehicle body side of a vehicle is made by bidirectional multiplex communication. Thus, not only a signal of the vehicle motion controller can be transmitted to the drive controller only by a signal line with a double core, but also information from a plurality of sensors provided for the drive controller can be transmitted to the vehicle motion controller. Therefore, the number of bending cables can be reduced and an object such that an inexpensive brake device is provided can be realized.
At this time, it is desirable that the signal line connecting the drive controller and the vehicle motion controller and an electric power line for supplying an electric power to the drive controller are constructed by a single cable covered with a same sheath in a portion connecting the vehicle body side and the wheel side. Thus, since the number of bending cables can be set to one, the object to provide an inexpensive brake device can be realized.
It is also preferable that the electric power line for the bending cable is a twisted pair-wire and the signal line is a coaxial wire. Thus, since an influence by noises exerted on a digital signal line by a DC power line is small, the electric power line can be constructed by a twisted pair-wire of a low cost. Consequently, the object to provide an inexpensive brake device can be realized.
It is desirable that communication information of the drive controller and the vehicle motion controller is transmitted by using the electric power line for supplying the electric power to the drive controller. Thus, since a core wire only for use in the signal line becomes unnecessary, the number of core wires in the bending cable can be reduced and the object to provide an inexpensive brake device can be realized.
It is also preferable that communication information of the drive controller and the vehicle motion controller is transmitted by radio communication. Thus, since a core wire only for use in the signal line becomes unnecessary, the number of core wires in the bending cable can be reduced and the object to provide an inexpensive brake device can be realized.
It is also preferable to electrically connect a wheel speed sensor for detecting a rotational speed of the wheel to the drive controller. Thus, the number of bending cables can be reduced and the object to provide a cheap brake device can be realized. Further, the drive controller can control the actuator at higher precision by using information of the wheel speed sensor.
It is also desirable to electrically connect a pad abrasion sensor for detecting abrasion of a brake pad to the drive controller. Thus, since a signal line only for use of a signal from the pad abrasion sensor does not need to be wired to the spring-mass, the number of bending cables can be reduced and the object to provide an inexpensive brake device can be realized. Further, the drive controller can control the actuator with higher reliability by using information of the pad abrasion detecting sensor.
It is also preferable to electrically connect a pneumatic sensor receiver for receiving a radio signal from an air pressure sensor provided for a tire to the drive controller. Thus, since a signal line only for use of a signal from the air pressure sensor does not need to be wired to the spring-mass, the number of bending cables can be reduced and the object to provide an inexpensive brake device can be realized. Further, the drive controller can control the actuator with higher reliability by using information of the air pressure sensor.
The above object is also accomplished by a construction such that the driver controller is arranged on the vehicle body side of a vehicle and, in a portion connecting the vehicle body side and the wheel side, the signal line connecting the drive controller and the actuator is constructed by one cable covered with a same sheath. Thus, since an expensive sheath is unnecessary every signal line, the object to provide a cheap brake device can be realized. Further, by constructing the power line and the signal line by the different cables, a cost which is necessary for a countermeasure against the noises can be reduced and a cheap brake device can be provided.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.